Many air actuated disc brakes, for use on heavy vehicles, have an adjuster mechanism to set the position of friction element to account for the wear thereof. Generally, the adjuster mechanism has an adjuster shaft of which an end portion is accessible from the exterior of the brake housing and is operable to manually re-wind or de-adjust the adjuster to permit removal of worn friction elements (commonly known as brake pads) and replacement thereof with new thicker elements and/or other servicing procedures.
In some installations air actuated disc brakes are also fitted with electrical continuous wear sensors (CWS) which monitor the amount of friction material remaining on the friction elements. This enables to the operator to monitor and plan for when the friction elements will need replacing.
In conventional adjuster mechanisms having such a continuous wear sensor, the sensor is mounted to the brake housing as a standalone unit that is located away from the manual adjuster. This results in a system wherein the continuous wear sensor takes up a relatively large amount of space in the brake housing. On disc brakes that do not use a CWS this space is redundant. In other brakes it is mounted to an exterior of the housing where it may be susceptible to corrosion and damage.
If excessive torque is used when manually re-winding the adjuster, the adjuster can become locked or jammed in the fully rewound end position. This can lead to reduced performance of the brake pads and/or torque generation by the brake pads, due to the clearance between the brake pads and the brake disc being too high to generate sufficient clamping of the brake disc. Similarly, if excessive torque is used to wind the mechanism forward to take up excess running clearance once new brake pads are fitted, the adjuster can be locked in an advanced position, potentially leading to overheating of the friction material of the brake pads and/or the rotor.
It is known to address this problem by using a “fuse” component on the adjuster shaft configured to shear off when excessive torque is applied and be easily replaced by a new fuse (e.g., that is provided with a set of new brake pads). It is also known to address this problem with the provision of instructions to the operator as to the maximum safe torque. However, a careless operator can ignore such instructions, or can inadvertently use excess torque, particularly if a power tool such as an impact wrench is used in re-winding or advancing.
In some installations, the brakes are also fitted with electrical continuous wear sensors (CWS) which monitor the amount of friction material remaining on the friction elements. This enables the operator to monitor and plan for when the friction elements will need replacing.
It is known for a continuous wear sensor to be mounted adjacent the adjuster shaft in a cast caliper housing of the disc brake, with apertures or recesses provided for each component. In existing arrangements, the housing has apertures or recesses for each component on three separate planes, and thus requires three separate machining operations after casting. In addition, the machined surfaces are devoid of protective coating, so require additional treatment to inhibit corrosion.
The present invention aims to alleviate or overcome the problems associated with the prior art.